1. Technical Field of the Invention
The present invention relates to an electrophographic image forming apparatus which enables printed output of a visible image on a recording medium by developing an electrostatic latent image on an image carrier through a development device.
2. Description of the Related Art
An image forming apparatus compatible with a color image has recently become widely prevalent. An image forming apparatus compatible with a color image have four development devices assigned to respective color components of YMCK, and a rotary (revolving body) unit around which the development devices are provided. In the image forming apparatus having such a configuration, the respective development devices integrally rotate in association with rotation of the rotary unit, whereby the development devices sequentially move to a development position where the development device faces a photosensitive drum which is an image carrier. Consequently, after having developed an electrostatic latent image on the photosensitive drum as a toner image, the development device located in the development position transfers the toner image to an intermediate transfer body, or the like. These operations are sequentially repeated such that the toner images formed by the respective development devices are superposed one on top of the other on the intermediate transfer body or the like, so that a transfer image corresponding to the color image is formed on the intermediate transfer body or the like.
In the electrophotographic image forming apparatus, the electrostatic latent image on the photosensitive drum is generally developed as a toner image. Accordingly, the concentration of toner, the amount of toner, and the amount of remaining toner, and the like greatly affect the image quality of a formed image. In view of this, an image forming apparatus, which has a rotary unit and is compatible with a color image, has hitherto been proposed to detect and monitor—through use of a custom-designed sensor, or the like—the concentration of toner, the amount of remaining toner, a determination as to whether or not the development device is attached to a predetermined position within the rotary unit, a determination as to whether or not a toner cartridge, which is a constituent unit of the development device, is attached, and the like, whereby the image quality of the formed image can be maintained well.
According to the above-related art, an image forming apparatus having a rotary unit requires rotation of the rotary unit in order to detect the state of a development device, such as the concentration of toner, the amount of remaining toner, and presence/absence of the development device, or the state of a constituent unit of the development device such as presence/absence of a toner cartridge. Specifically, separately from rotation of the rotary unit required by each development device in the rotary unit to develop an electrostatic latent image on the photosensitive drum, rotation of an individual rotary unit for detecting the state of each development device or the state of a constituent unit of the development device is required. Consequently, the productivity achieved through image formation may be degraded by an amount corresponding to the time required by the individual rotary unit to rotate.